/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: Lenovo
 * Date: 2025-05-24
 * Time: 14:57
 */
public class Test {
    public static void main(String[] args) {
        int n=1;
        int sum=0;
        for (int i = 1; i <= 20; i++) {
            n*=i;
            sum+=n;
        }
        System.out.println(sum);
    }
}
